US1813649A - Dehydration and decomposition of iron sulphates - Google Patents

Description

Pas ed July 1, 1931 UNITED STATES PATENT OFFICE PAUL WEISE, OI WIESDOBF-ON-IHE-BHINE, GEBI ANY, ASSIGKOR '10 1'. G. FABBEN OF rmxronr-oN-rnn-m, GERKAJNY, A

INDUSTBIE AKTIEN'GESELLSCHAFT, CORPORATION OI GEBM'ANY DEHYDBA'IION AND DECOMEOSITION 0! IRON SULPH Am Io Drawing. Application filed January 5, 1929, Serial No. 830,621, and in Germany January 9, 1928.

The present invention relates to a process for the dehydration and decomposition of iron sul hates. i

The d ehydration and decomposition of the ferrous sul hate, crystallizing with seven molecules'of water, proceeds in three stages, if this compound is heated in an oxid zmg atmosphere such as air; first, thesalt is dehydrated, then the salt oxidizes to form ferr1c salt, and then the ferric salt decomposes to form S0 and ferric oxide.

The technical dehydration and decomposition of iron sulphates, especially of ferrous sulphate FeSO 7H O, in mechanical ovens sufiered from various disadvantages up to this day.

As FeSOJH O, when being dehydrated,

1 melts in its own water of crystallization, me-

chanical ovens, especially the rotary furnace, could not be used heretofore, since either the melted mass passed unhindered through the rotary furnace or adhered tenaciously to the wall and caused the oven in a short time to smear or become greasy and clog up. For these reasons, it has also been impossible to carry out any oxidation process subsequent to the dehydration or subsequent to the-decomposition. Furthermore, the processes suffered from the disadvantage that decomposition roducts, as SO dissociated into S0 and 2 on account of the high decomposition temperature; Consequently, only poor yields of S0 could be obtained. I 1

According to the present inventionthese disadvantages are removed by adding to the 'ferrous sulphate to be dehydrated a substance which dlmlnishes the plasticity and which does not prejudicially interfere with the kind and quality of the solid decomposition prodnot, the most favorable substance for the purpose of my invention being the partially dehydrated ferrous sulphate of the formula: FeSO .1H O, or ferric oxide, which latter acts in myprocess at the same time as an oxidizing catalyst. The quantity of the substance diminishing the plasticitymay be varied within wide limits, at least about 10% calculated on the amount of the ferrous sulphate bein required generally, I add an amount of om about 10% to about 30%. 7

As the S0,, evolved at the decomposition temperature of the ferric salt, partially dissociates in'to S0 and 0 an oxidizing catalyst to 5%, such as an-alkalior alkaline earth metal oxide, hydroxide or carbonate, whereby an eva oration of the sulfuric acid is hindered; ee sulfuric acid would unfavorably influence the quality of the ferric oxide obtained in my process.

My process may preferably be performed in a rotary furnace, in which the upper part acts as dehydrating .zone, the medium part as oxidizing zone, and the lower parts as decomposing zone. The best results are obtained in using at least three separated rotary furnaces, the first furnace being heated to-a temperature of from about 100 to about 200 C. and serving to dehydrate the ferrous sulphate to form F eSO H O, the second furnace being directly heated with oxidizing gases to about 300 to 400 C. and serving to form ferric sulphates, and the third rotary furnace being indirectly heated to about 750 to about 800 C.

According to my process it is possible to work up ferrous sulphate in a. mechanical oven into ferric oxide suitable to be used as a pigment and to recover almost completely the sulfuric acid in the form of S0 The invention is illustrated by the following examples, without being limited thereto:

ing, the mixture is placed in a second rotary furnace in which it is slowly heated through one or more stages and 1n an oxidizing atmosphere up to a temperature of about 300 to 400 0., to form ferric sulphate. The ferric compound is placed in a thlrd rotary furnace wherein it is indirectly heated to the decomposition temperature of the ferric salt, for instance to 750 to 830 0. Llght iron oxide, suitable to be vused as a igment, is obtained and at the upper end 0 the rotary furnace SO escapes.

E wmmple 2.Ferrous sulphate (FeSO 7H O) (with the addition of FeSO, or 25% FeSO .1H O is mixed with 1% of sodium carbonate and, depending on'the amount of F eSO.or.FeSO .1H O further, is mixedwith 10-30% by weight of-iron oxide and treated as described in Example 1.

I claim 1. In the process for the dehydration and decomposition of iron sulphates the step which comprises heating a mixture of Iron sulphate and 10-30% of a solid, iron-containing decomposition product of lron sulphate, to a temperature of between about 100-200 0.

2. In the process for the dehydratlon and decomposition of iron sulphates the step which comprises heating a mixture of iron sulphate and 10-30% of a solid, iron-containing decomposition product of iron sulphate, to a temperature of between about 100200 0. in a rotary furnace.

3. In the process for the dehydration and decomposition of iron sulphate the step which comprises heating a mixture of iron sulphate and 10-30% FeSO .1H O to a temperature of between about 100-200 0.

t. In the process for the dehydration and decomposition of iron sulphate the step which comprises heating a mixture of iron sulphate and 10-30% FeSO .1H O to a temperature of between about 100-200 0. in a rotary furnace.

5. The process decomposition of iron sulphates which comprises heating a mixture of iron sulphate and 10-30% of at least one solid, iron-containing decomposition product of iron sulfate, to a temperature of between about 100-200 0., heating the dehydrated mixture in an oxidizingatm'osphere to a temperature of between about 300-400 0. in the presence of anoxidizing catalyst, and heating the oxidized mixture to a temperature of between about 750830 0.

6. The process for the dehydration and decomposition of iron sulphates which comprises. heating a mixture of iron sulphate and 10-30% of a mixture of FeSO .1H O

and iron oxide (Fe O to a temperature of between about 100-200 0., heating the dehydrated mixture in an oxidizing atmosphere to a temperature of between about 300-400 0., and heating the oxidized mixfor the dehydration and ture to a temperature of between about 750-830 0.

7. The process for the dehydration and decomposition of iron sulphates which comprises heating a mixture of iron sulphate and 10-30% of at least'one" solid iron-containing decomposition product oi iron sulphate, to a temperature of between about 100-200 0., heating the dehydrated mixture in an oxidizing atmosphere to a temperature of between about 300-400 0. inv the presence of an oxidizing catalyst, and heating the oxidized mixture to a temperature of between about 750-830 0., the three heating processes being efiected in rotary furnaces.

8. The .process for the dehydration and decomposition of iron sulphates which comprises heating a mixtureof iron sulphate and 10-30% of a mixture of FeSO II-I O and-iron oxide (Fe O to a temperature of between about 100-200 0., heating the demy hand.

PAUL WEISE. [net]